Safety device for gas heaters



P 13, P. L. BETZ El AL 2,130,175

SAFETY DEVICE FOR GAS HEATERS Filed' Aug. 50, 1935 TO CONTROL sYs.

Patented ept. E3, 193

SAFETY DEVICE FUR GAS HEA'EERS Application August 30, 1935, Serial No. 38,654

ll Claim.

This invention relates to safety devices for gas burners as for example in the ordinary household gas heater for heating water or for other purburner, controlling or actuating means for regulating the position of the valve which means are thermally controlled so that said valve is closed automatically in case of flashback, but said Poses means are thereafter restored to normal operat- Gas heaters of conventional types are subject ing condition for regulating the position of the 5 at times to what is known in the art as a rlashvalve. back. Such heaters usually comprise a gas Another object is to provide, in combination burner, the gas being mixed with air in a mixwith an electrically operated valve controlling ing chamber adjacent the burner and the comthe gas supply to a burner, an energizing valve bustible mixture of gas and air being conducted circuit having thermally responsive regulating w to the burner where it is ignited by means of a means which are subjected to the temperature pilot. At times the flame flashes through the in the mixing chamber supplying the mixture of burner ports and the gas burns in the chamber gas and air to the burner and are arranged to where the mixture or air and gas normally takes control said circuit in such a way as to cause place. When such a flashback occurs, the gas the closing of the valve in the event of flashback. l5 often burns with insumcient oxygen resulting in One embodiment of the invention has been the production of a relatively large quantity of illustrated in the accompanying drawing, but carbon IilOllOXldB, and for this reason such deit is to be expressly understood that said drawvices are conventionally provided with this coning is for purposes of illustration only and is not nections. To prevent the danger incident to the to be construed .as a definition oi'th'e ts oi 20 production of carbon monoxide and to minimize the invention, reference being had to the apthe need for ilue connections, it is desirable to p n d cl im for this purncs In said draw provide safety means whereby the gas supply is ing: shut ofi' in the case of a flashback. In order Fig. l is a diagrammatic illustration of a gas that such devices may have maximum utility water heater and connections thereto which is as and advantage, particularly in the case of autoequipped with electrical control means embodymatic appliances, it'is further necessary that ing the invention; the safety means employed be of such nature as Fig. 2 is a perspective view oi the thermally to restore the system automatically to normal responsive control element of Fig. 1; operating condition alter the gas has been shut Fig. 3 is a sectional view of said thermally so off. responsive element.

Cine oi the objects of the invention is to pro= Generally speaking, the invention embodies a vide means in combination with a gas burner thermally responsive element which is subjected which means operates automatically in case of to temperature conditions erdsting in the mixflashback, first to shut oil the gas supply and ing chamber wherein the mixture of gas and air 35 then to restore the system to operating contakes place. Since in the event of flashback the dition. mixing chamber is subjected to abnormal tem- Another object is to provide novel means reperature, a thermally responsive element subsponsive to thermal conditions existing in the jected to this temperature can be employed in mixing chamber for controlling the supply of the event of flashback to regulate a suitable gas so combustible mixture to the burner. control valve. This valve may be either a spe- A further object is to provide thermally conclal safety valve, or in an automatically operating trolled valve means fora gas burner which means system the supply valve of the system may be is movable automatically to open or closed controlled by said thermally responsive means positions according to the thermal condition in addition to the normal control thereof by the o5 existing in the mixing chamber supplying the usual or any suitable automatic devices. The mixture of g s d air t0 the immerthermally responsive element is located in the A still further object is to provide, in commixing chamber, and any suitable form of therbination with a valve regulating the gas supply rnostatie device may be employed depending to a burner, a novel thermostatic means exposed upon conditions of use, such as bimetallic mern- 50 to heat resulting from a flashback for moving the hers, collapsible and expansible members, etc. valve to closed position. Further, the means whereby the valve is actu- Another object is to provide, in combination ated or controlled by the thermally responsive with a valve regulating the gas supply to a means is here shown as electrical of standard type used with the control system to be employed for the heater. With such an electrical system, various control devices and circuits may be em-' ployed, and the particular manner in which a device embodying the present invention is to be used will depend on the nature of such control systems. For example, in systems embodying electrically' controlled or operated valves, the device may be connected in series in the valve circuit. On the other hand '"here an electrical valve control system is employed which embodies other valve control devices such as relays, the flashback control may be utilized to prevent the normal operation of such control devices and in turn of the supply valve.

Oneillustrative embodiment of the invention has been shown in the drawing. Figs. 1; 2 and 3 illustrate the embodiment of the invention applied to a heating system which is electrically controlled, the thermally responsive element being located in the mixing chamber. Referring to Fig. 1, a gas water heater of any suitable type is conventionally illustrated, this heater comprising a shell I supported on legs 2 and enclosing a coil 3 having an inlet connection 4. Water passing through the coil is heat'edby means of the gas burner 5 supplied with gas through pipe 6 in which is incorporated a control valve 1. As indicated above, this valve 1 may comprise the main supply valve of'the system, which in an automatic system is controlled by known or any suitable devices, or it may comprise a special safety valve which is closed only in the event of a flash back. When the valve is open, gas passing through the pipe 6 enters a mixing chamber 8 which, as shown, is of conventional form and in which the gas is mixed with air entering said chamber through one or more ports 9. The combustible mixture of gas and air passes from the mixing chamber to the burner 5 through a conduit II], where it is ignited by the usual or any suitable pilot device Illa. It will be understood that the particular design and details of the system as thus far described constitutes no part per se of the present invention.

As shown in Fig. 1, the valve 1 is electrically controlled through the leads I l. Electrically operated valves of various types are known and can be obtained on the market. One suitable type of valve comprises an operating electromagnet which holds the valve open against spring tension during operation of the system, the spring restoring the valve to closed position when the electromagnet is deenergized, and this type of valve is assumed in the following description. In the event that valve 1 is the main supply valve of an electrically controlled automatic system, the supply of current through the leads H to the valve will be controlled by any suitable automatic system which may be connected to the leads II in any suitable mannen Since the details of such systems constitute no part of the present invention, thecontrol circuits are not shown or described herein.

The details of construction of a suitable thermally responsive device comprising a bimetallic thermostat are shown in Figs. 2 and 3. The thermally responsive device may be mounted in any suitable manner and as shown is supported by a bracket l2 secured to one of the legs 2 of the heater. As shown in detail in Figs. 2 and 3, the device comprises a plurality of blocks of any suitable material l3 and a support I4 which are assembled by means of the screws I5. The blocks I3 support a pair of resilient arms I6 01 conductive material provided at one end with suitable terminals I! to which the leads II are connected and at the other endv with contact members I8, said arms being .insulated from the supporting blocks in any suitable way. If the blocks are of conductive material such as metal, interposed strips of mica or other insulation can be employed, or the blocks themselves may be made of insulating material.

As stated above, the contacts 18 can be utilized to control a circuit which, either directly or indirectly through other control devices, causes the valve to be maintained open to permit the flow of gas to the burner. In the form shown, for example, the contacts l8 are in series with the valve and the arms l6'are so arranged that they tend to maintain the contacts l8 open. When the contacts are held in closed position as shown in Fig. 3 and as described hereinafter, they complete the circuit of the valve 1, and when said contacts are permitted to open, the circuit of the valve is interrupted, the electromagnet is deenergized, and the valve closes, shutting oi! the supply of gas.

The support 14 is provided with an angularly extending arm l9 which passes through one of the air ports 9 and thus extends within the mixing chamber 8. Secured to the upper end of the arm IS in any suitable manner, as by means oi. a screw 20, are an L-shaped block 2| and a cooperating block 22 both of which are preferably of metal having relatively high heat conductivity. A suitable thermostatic element in the form of a bimetallic strip 23 is secured between the blocks 2| and 22. An arm 24 secured to the end of the bimetallic strip 23 passes through a guide slot 25 in the support l4 and is adapted through any suitable mechanical connection to operate the contacts l8. Thus said arm 24 may be arranged to move one of the arms IE to and fro whereby said contacts are both opened and closed by the arm 24, but where said arms l6 are resilient as described above, it is suflicient to provide arm 24 at its end with a block 26 of suitable insulating material which bears against one of the resilient arms J6 and normally maintains the contacts I! closed as shown in Fig. 3.

Under normal conditions of operation of this system, the temperature within the mixing chamber 8 is relatively low and the contacts I8 are maintained closed by the bimetallic strip 23 so that they have no eifect on the operation of the valve I by any control system which it is desired to employ. However, in the event of a flashback, the temperature within the mixing chamber is increased by reason of the gas flame which burns at the end of the supply pipe 6 within the chamber. The thermostatic element, which is preferably located close to this flame, is heated thereby and bends in such direction as to move the arm 24 and the block 26 away from the resilient arm I6. Said arms thereupon spring apart by virtue of their own resilience, opening the contacts I8 and interrupting the circuit to the valve 1 which then closes and-shuts ofl the gas supply. However, as soon as the temperature within the mixing chamber returns to normal, which ordinarily takes place within a short interval, the bimetallic strip 23 cools off and moves the arm 24 back until the contacts l8 are again closed and the system is thereby restored to condition for operation in normal manner through the control devices which are provided for the system.

It will be perceived that the invention provides a safety device which is automatically operative to stop the flow of gas to the burner in the event of a flashback and which is also automatically operative thereafter to restore the system to normal condition for operation by any of the usual control means that may be provided. The invention thus has the advantage or providing an effective safety device while at the same time interfering in'no way with the normal or any desired control or operation of the heating system, except in the event of flashback and only so long as an abnormal temperature prevails. The danger incident to the production of carbon monoxide in the event of flashback is eliminated by the invention, and in the case of automatically controlled and operated systems, flue connections are unnecessary. These results are accomplished by a simple, inexpensive device which is at the same time dependable and reliable in operation.

In the case of an automatic or semi-automatic system, the feature of restoring the system to normal operative condition in an automatic manner is particularly advantageous. Safety devices which merely shut off the supply of gas, as by thefusing of a metallic link or some equivalent operation, usually require the services of a skilled mechanic in order to restore the systemto operating condition, which results in the system being inoperative and useless for considerable periods of time.. Devices embodying the present invention, however, incorporate the desired safety feature in the system in an effective and dependable operation, while at the same time they permit renewed operation of the system immediately after the flashback has been extinguished and without attention or manual adjustment. In the event of flashback, the interruption of service is, thereby, only temporary.

While one embodiment of the invention has been described and illustrated in the drawing, it is to be expressly understood that the invention is not limited thereto, as-ohanges may be made in the form, details of construction and ar rangement of the various parts, while equivalent thermostatic devices may be substituted for that described and illustrated, all without departing from the spirit of the invention. Thus, any suitable type of thermostatic element may be used in place of the bimetallic strip f Figs. 1-3 to operate the electric contacts involved in these systems. Further, the manner of installation of the thermostatic element and the operating mechanism actuated thereby may be varied widely. Reference is, therefore, to be had to the appended claim for a definition of the limits of the invention.

What is claimed is:

In a device of the class described, the combination of a burner, means for mixing gas and air and supplying the mixture to said burner, an electrically controlled gas supply valve, an energizing circuit for said valve, a pair of contacts controlling said circuit and disposed outside said mixing means and not subject to heat therefrom, a frame carrying said contacts and having an arm extending into said mixing means, and a bimetallic element carried by said arm within said mixing means and exposed to heat from a flame therein, said element being operatively connected with said contacts to operate the same.

PAUL L. BETZ. SEBASTIAN KARRER. 

